A known accelerator device has an electronic configuration to cause a sensor to detect a depression quantity of an accelerator pedal and to transmit an electric signal, which represents the depression quantity, to an electronic control unit. Patent Document 1 discloses an accelerator device. The accelerator device includes a frictional member, which is equipped between a pedal arm of an accelerator pedal and a spring rotor. The frictional member has an annular portion and a rotation restrictive projected portion. The annular portion is slidable relative to the pedal arm. The rotation restrictive projected portion is projected from the annular portion outward in the radial direction. The projected portion has a tip end, which is fitted to a recessed portion formed in a wall of a housing to restrict relative displacement in the rotational direction.
(Patent Document 1)
Publication of Unexamined Japanese Patent Application No. 2006-032712 It is noted that, each of components of the accelerator device increases and decreases in size with change in temperature of an operation environment. In general, the frictional member is formed of a resin material, which is relatively soft, and the housing is formed of a resin material, which is relatively hard. Further in general, the relatively soft resin material has a coefficient of linear expansion greater than a coefficient of linear expansion of the relatively hard resin material. Therefore, the projected portion of the frictional member expands under an operation environment at high temperature, such that the projected portion is urged onto the wall of the housing. After the projected portion is continually urged onto the wall of the housing, the projected portion causes a creep strain. Consequently, the projected portion of the frictional member reduces in size at a contact portion at which the projected portion is in contact with the wall of the housing. As a result, when the operation environment decreases to a relatively low temperature, a gap may be formed between the projected portion of the frictional member and the wall of the housing. Thus, even when a driver depresses the accelerator pedal, depression force may not appropriately increase in the beginning of the depression due to the gap. Consequently, the formation of the gap may impair an operational feeling of the accelerator pedal.